INTRODUCTION

Laelaps petrischevae Zemskaya et Lange, 1979, an ectoparasitic gamasid mite infests small mammals of the Yamal Peninsula (the north of Western Siberia) and northern regions of Middle Siberia (Zemskaya and Lange 1979). However, since its description the species has not been men-tioned in papers devoted to the gamasid mites fauna of northern Siberia (El’shin 1992; Mal’kova 2005, 2010). It also is omitted in the resumptive monograph “Gamasid mites of Western Siberia” (Davydova and Nikolsky 1986) as well as in the catalogue of parasitic gamasid mites of Northern Eurasia compiled by Nikulina (2004). The origi-nal description of L. petrischevae is until now the only source of information on its morphology, taxonomic position, bionomics and host range.

Having examined a vast collection of ectopar-asitic gamasid mites from small mammals of the Yamal Peninsula, we obtained some new data about species of the genus Laelaps C.L. Koch, 1836 of this region that allow us to clarify the tax-onomic position of L. petrischevae.

MaTeRIals aND MeThODs

We examined collections of gamasid mites sampled in the southern subarctic tundra zone of the Yamal Peninsula (samples made by Drs. V.V. Yakimenko and M.G. Mal’kova, Omsk Research Institute of Natural Foci Infections, ORINF here-after). The mites were taken in 2005 from Mid-dendorff’s voles (Microtus middendorffi Poljakov, 1881). Voucher specimens are kept in the Museum of Medical Arachnoentomology of ORINF.

For the comparative purposes, collections of mites of the genus Laelaps of some scientific insti-

tutions of Russia were used. We examined mites from acarological collections of the Zoological In-stitute of the Russian Academy of Sciences (Saint Petersburg, ZIN hereafter), the Department of En-tomology of the Moscow State University (Mos-cow, MGU hereafter), the N.F. Gamaleya Research Institute of Epidemiology and Microbiology (Moscow, GRIEM hereafter), and the Institute of Systematics and Ecology of Animals of the Sibe-rian Branch of the Russian Academy of Sciences (Novosibirsk).

Mite measurements were made by using Mikmed-1 microscope. In total, 17 females and 2 males of Laelaps alaskensis from the Yamal Pen-insula were measured. 18 measurements of exter-nal skeleton were taken from each female. These measurements serve for characterization of main elements of external skeleton of mites which in-cludes in Laelaps females four shields (dorsal, sternal, epigynal and anal). The scheme of female measurements includes: (1–2) length and width of the dorsal shield (LD and WD respectively); (3) length of the sternal shield in the middle (LS); (4–5) width of the sternal shield between its ante-rior and posterior ledges (WS1; WS2); (6–8) dis-tance between sternal shield setae in pairs (DSt1–St1, DSt2–St2, DSt3–St3); (9) length of the epigynal shield (LE); (10) width of the epigynal shield ahead of its broadening (WE1); (11) width of the epigynal shield in its widest part (WE2); (12–15) distance between epigynal shield setae in pairs (DGen–Gen; DZv1–Zv1; DJv1–Jv1; DJv2–Jv2); (16–17) length and width of the anal shield (LA; WA); (18) distance between of the paranal setae (DparA–parA). Also, we measured the lengths of setae on the dorsal and the ventral

Acarina 20 (1): 29–35 © Acarina 2012

TaXONOMIC sTaTUs OF LAELAPS PETRISCHEVAE ZeMsKaYa eT laNGe, 1979 (aCaRI: PaRasITIFORMes: GaMasINa)

N. P. Korallo-Vinarskaya1,2 and M. V. Vinarski3

1 Laboratory of Arthropod-Borne Viral Infections, Omsk Research Institute of Natural Foci Infections, Mira str. 7, 644080 Omsk, RussIA, e-mail: vinarskayan@inbox.ru2 Omsk Branch of the All-Russia Institute of Textile & Light Industry, Pushkin str., 63, 644010 Omsk, RussIA3 Department of Zoology and Physiology, Omsk state Pedagogical university, Tukhachevskogo emb. 14, 644099 Omsk, RussIA, e-mail: radix.vinarski@gmail.com

ABSTRACT: Laelaps petrischevae Zemskaya et Lange, 1979 was described ex Microtus voles from the northern parts of West-ern and Middle Siberia. However, the species has not been mentioned later in taxonomic and faunistic papers dealing with the ectoparasitic gamasid mites of Siberia. Examination of newly collected laelapid mites from the Yamal Peninsula as well as the comparison with the published data led to conclusion that L. petrischevae Zemskaya et Lange, 1979 (syn. n.) is a junior synonym of L. alaskensis Grant, 1947. Key for identification of females of the Laelaps species inhabiting the northern regions of Western and Middle Siberia is given.

KEY WORDS: gamasid mites, Laelapidae, Laelaps petrischevae, Laelaps alaskensis, synonymy, identification key

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shields (Lj1, LZ4, LSt1, LSt2, LSt3, LGen, LZv1, LJv1, LJv2).

The males were measured under the reduced scheme as compared with the females. Only length and width of the dorsal shield was taken. Besides, the length of the legs (LLI, LLII, LLIII, LLIV) was determined in individuals of either sexes.

The setal nomenclature follows Lindquist and Evans (1965), Evans and Till (1966, 1979).

ResUlTs aND DIsCUssION

According to the statement of the authors of L. petrischevae (Zemskaya and Lange 1979), the type series consists of two specimens (holotype and paratype) collected from Microtus gregalis (Pallas, 1779). The type locality is designated as “Yamal Peninsula, valley of the Schchuchya Riv-er”. Another known locality of this species men-tioned by Zemskaya and Lange (1979) is the vi-cinity of Norilsk City (north of Middle Siberia). It was stated that the type specimens are kept in the GRIEM collection (Zemskaya and Lange 1979). Unfortunately, we were not able to find these spec-imens in GRIEM in May of 2007, and, most prob-able, the types of L. petrischevae are lost (E.I. Ko-renberg, personal communication). Zemskaya and Lange (1979) pointed that certain additional spec-imens of L. petrischevae were given to the ZIN and MGU collections. We failed to find any mate-rials on L. petrischevae in the both of collections mentioned. Thus, there are no specimens of this species in the acarological collections available to us and therefore we can judge about its taxonomic position only on the ground of data published in the original description.

The analysis of these data allowed us to sug-gest that L. petrischevae is no other but a synonym of Laelaps alaskensis Grant, 1947, first described from North America (type locality — Jack River, Alaska; see Tipton 1960) and later found in West-ern Siberia (Davydova and Nikolsky 1986).

The grounds in favor of such opinion are as follows.

1. Morphological similarity. The original picture of L. alaskensis (Fig. 1) is somewhat sketchy; it does not give the full information about details of its external morphology. The illustration of L. alaskensis given by Tipton (1960) exhibits more characters of a taxonomic value. Davydova (1968) also gives some morphological informa-tion (including illustrations) about L. alaskensis found in Western Siberia. Comparing the data from the original description of L. petrischevae

with the data on L. alaskensis morphology (figs. 2–3), following similarities between these species could be mentioned.

Female. Sternal shield (Fig. 2). The shape of the sternal shield in both species is typical for the genus Laelaps. Its width is nearly two times larger than the length (Table). The posterior margin of the shield is concave. The shield bears three pairs of sternal setae (see Table), and their location is typical for the genus Laelaps. The first pair is situ-ated on the front margin of the shield and their tips almost reach its posterior margin.

Epigynal shield (see Fig. 2, Table). The shape of the shield as well as an assortment and location of the setae are characteristic for the genus Lael-aps. In the two species under comparison, the ven-tral part of the epigynal shield is sharply widened on the level of the genital setae (gen). The poste-rior margin of the shield is almost straight or slightly concave between the fourth pair of setae. The pattern of shield ornamentation is also analo-gous in L. alaskensis and L. petrischevae. The front margin of the shield is continued in a folded membrane.

Anal shield (see Fig. 2). The shield is of near-ly triangular shape, its margins are well sclero-tized. The paranal setae are positioned below the posterior margin of the anal opening and are much longer than the latter. The postanal seta is long and strong.

In both species there are rather strong opist-hogastric setae beyond the plates. These setae are not equal in their length and thickness.

Fig. 1. L. alaskensis (after Grant 1947). sh — shoulder.

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Taxonomic status of Laelaps petrischevae

Character* Limits of variation Mean ± standard deviation (σ)LD 0.57–0.64 0.59 ± 0.01WD 0.41–0.47 0.45 ± 0.02Lj1 0.01–0.02 0.02 ± 0.01LZ4 0.12–0.14 0.13 ± 0.01LS 0.07–0.09 0.09 ± 0.01

WS1 0.17–0.20 0.19 ± 0.01WS2 0.23–0.25 0.24 ± 0.01

LS/WS2 0.33–0.40 0.38 ± 0.02DSt1–St1 0.07–0.09 0.09 ± 0.01DSt2–St2 0.14–0.17 0.16 ± 0.01DSt3–St3 0.15–0.18 0.17 ± 0.01

LSt1 0.08–0.09 0.09 ± 0.01LSt2 0.09–0.1 0.09 ± 0.01LSt3 0.08–0.1 0.09 ± 0.01LE 0.26–0.29 0.28 ± 0.01

WE1 0.17–0.19 0.18 ± 0.01WE2 0.23–0.24 0.24 ± 0.01

DGen–Gen 0.13–0.14 0.14 ± 0.01DZv1–Zv1 0.18–0.20 0.20 ± 0.01DJv1–Jv1 0.14–0.16 0.15 ± 0.01DJv2–Jv2 0.07–0.09 0.08 ± 0.01

LGen 0.08–0.09 0.09 ± 0.01LZv1 0.09–0.10 0.10 ± 0.01LJv1 0.09–0.11 0.10 ± 0.01LJv2 0.09–0.11 0.10 ± 0.01LA 0.11–0.13 0.12 ± 0.01WA 0.09–0.1 0.10 ± 0.01

DparA–parA 0.03–0.05 0.04 ± 0.01LLI 0.36–0.39 0.37 ± 0.01LLII 0.32–0.36 0.34 ± 0.01LLIII 0.32–0.36 0.35 ± 0.01LLIV 0.48–0.55 0.50 ± 0.02

TableMeasurements of Laelaps alaskensis female (n = 17) from the south of Yamal Peninsula (in millimeters)

*For abbreviations decoding see Material and Methods

Dorsal shield (Fig. 3). It is of ovoid shape, with clearly pronounced shoulders. The setae on this shield are of similar appearance (all needle-shaped), but some anterior pairs smaller than oth-ers and the length of marginal setae increases pos-teriad. j1 setae have the minimum length, and Z4 setae — maximum one (see Table).

Legs. Judging from the published data, the coxal armament also is similar in L. alaskensis and L. petrischevae. Coxa II bears one thickened seta of spicular shape and another hook-like one. Legs IV are the most thin and long (see Table). The for-

mula of genu IV is . The apical setae of tarsi II–III are thickened.

Male (Fig. 5). Smaller and more slender as compared with female (size of the dorsal shield is 0.56–0.64 mm × 0.35–0.41 mm, its shape is identical with that in female), and our results correspond well to the literary data (Grant, 1947). Legs II are some-what thicker than all the rest, legs IV are the longest (I 0.37–0.47 mm, II 0.34–0.36 mm, III 0.37–0.41 mm, IV 0.53–0.55 mm). Tarsi IV with four thickened setae, of which pl1, pl2, av1 are short and spicular (Fig. 6). The spermatodactyl is illustrated on Fig. 7.

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At last, the body sizes of both species should be compared. Zemskaya and Lange (1979) report-ed that LD in L. petrischevae is equal to 0.60–0.64 mm, and WD varies between 0.45 and 0.50 mm. L. alaskensis from the southern Yamal demon-strate almost the same values of LD and WD (Ta-ble). In North America, LD in L. alaskensis is 0.57 mm and WD is 0.465 mm (Grant 1947). Hence, there are no clear distinctions in absolute sizes of the two mite species.

2. Ecological similarity. It is known that the mites of the genus Laelaps are mostly mono- or oligohostal parasites with limited range of hosts

(Zemskaya 1973; Korallo 2004, 2005). Hence, the similarity between sets of small mammals parasitized by L. alaskensis and by L. petrische-vae may serve as an indirect evidence for their conspecifity. According to Zemskaya and Lange (1979), the hosts of L. petrischevae are several species of Microtus vole (M. middendorffi Polja-kov, 1881, M. oeconomus Pallas, 1776, M. grega-lis) as well as two lemming species (Lemmus si-biricus Kerr, 1792, Dicrostonyx torquatus Pallas, 1778). Besides, the species has been (accidental-ly?) found in Sorex shrew (Zemskaya and Lange 1979).

A B C DFig. 2. Laelaps spp., female, ventral view; A — L. petrischevae (after Zemskaya and Lange 1979), B — L. alaskensis (after Tipton 1960), C — L. alaskensis (after Davydova 1968), D — L. alaskensis (original; Southern Yamal, bank of the Yerkuta-Yakha River). Scale bars: 0.1 mm (B, D). Scale bars are absent in the original papers (A, C).

A BFig. 3. Laelaps spp., dorsal view; A — L. petrischevae (after Zemskaya and Lange 1979), B — L. alaskensis (after Tipton 1960). Scale bar 0.1 mm (B), or absent in the original paper (A).

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Taxonomic status of Laelaps petrischevae

L. alaskensis possesses, in essence, the same circle of small mammal hosts in the Eurasiatic part of its range. It is recorded from Microtus voles (M. middendorffi and M. gregalis) as well as from red-backed vole (Clethrionomydis rutilus Pallas, 1779) and tundra shrew, Sorex tundrensis Merriam, 1900 (Zemskaya 1973; Davydova et al. 1980; Davydo-va and Nikolsky 1986). We found L. alaskensis in the mite collection sampled in the southern Yamal from M. middendorffi. Mal’kova (2010) believes this vole species to be the main host of L. alasken-sis in the Yamal Peninsula.

3. Geographical distribution. Only two re-cords of L. petrischevae are known to the date. Both of these are located in the northern part of Siberia northward to the Polar circle (Zemskaya and Lange 1979). The geographical distribution of L. alaskensis in Palearctic is confined to the rela-

tively narrow band from the Komi Republic east-ward to Yakutia (Zemskaya 1973; Davydova et al. 1980; Davydova and Nikolsky 1986; Mal’kova 2010). Therefore, the range of L. petrischevae is much less than that of L. alaskensis and is situated within the borders of the latter.

All the considerations above brought us to conclusion that there are no morphological or eco-logical differences between the two species, and their ranges of distribution are overlapping. We regard L. petrischevae (syn. n.) to be a junior syn-onym of L. alaskensis.

Key for identification of females of the Lael-aps species inhabiting the arctic and subarc-

tic regions of Western Siberia

1 (2) Anal shield ovoid. Adanal setae situated be-hind anal opening (Fig. 4 A) ............................................................................. L. lemmi Grube, 1851

A B C

D E

Fig. 4. Laelaps spp., female, certain diagnostic features used for identification purposes: A — L. lemmi, ventral view (after Bregetova 1956); B — L. hilaris, ventral view (after Bregetova 1956); C — L. semitectus, dorsal shield (after Grokhovskaya 1960); D — L. semitectus, ventral view (after Grokhovskaya 1960); E — L. clethrionomydis, ventral view (Bregetova 1956).AS — anal shield; ES — epigynal shield ; CX II–III — coxae II–III; DS — dorsal shield; StS — sternal shield; parA — paranal setae.

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2 (1) Anal shield triangular. Adanal setae situated at level of posterior margin of anal opening (Fig. 4 B).3 (4) Dorsal shield with well developed shoulders and setae thickened (see Fig. 1, 3 A) ....................... .......................................................... L. alaskensis4 (3) Dorsal shield without pronounced shoulders, its setae not thickened (Fig. 4 C).5 (6) Epigynal shield smoothly widened between transversal levels of setae gen. and Zv1. Distance between gen.–gen. almost equal to distance be-tween Jv2–Jv2 (Fig. 4 B) ........................................................................... L. hilaris C.L. Koch, 18366 (5) Epigynal shield sharply widened between transversal levels of setae gen. and Zv1. Distance between gen.–gen. significantly more than dis-tance setae between Jv2–Jv2 (Fig. 4 D, E)7 (8) Ratio between length (in central part) and width (at level of posterior ledges) of sternal plate 1.5–1.6 (Fig. 4 D) ................................................................................ L. semitectus (L. Koch, 1878)8 (7) Ratio between length and width of sternal plate is 2.0 and more (Fig. 4 E) ........................................................ L. clethrionomydis Lange, 1955

ACKNOWLEDGEMENTS

The authors wish to thank Dr. Prof. Edward I. Korenberg (Moscow, GRIEM) and Dr. Maria K. Stanyukovich (Saint Petersburg, ZIN) for permis-

sion to work with acarological collections. Also authors are grateful to Dr. Olga L. Makarova (Moscow, Severtsov Institute of Ecology and Evo-lution of the Russian Academy of Sciences) and Dr. Irina I. Marchenko (Novosibirsk, Institute of Systematics and Ecology of Animals of the Sibe-rian Branch of the Russian Academy of Sciences) for sending us copies of some taxonomic papers devoted to the genus Laelaps. We thank Dr. V.V. Yakimenko and Dr. M.G. Mal’kova (Omsk Re-search Institute of Natural Foci Infections) pro-vided mites from the Yamal Peninsula for the study.

ReFeReNCes

Davydova, M.S. 1968. Gamazovyye kleshchi Zapadnoy Sibiri [Gamasid mites of Western Siberia]. MS thesis. Institute of Biology of the Siberian Branch

Fig. 5. L. alaskensis, male, ventral view (original; Southern Yamal, bank of the Yerkuta-Yakha River). Scale bar 0.1 mm.

Fig. 6. Laelaps spp., male, tarsi IV: A — L. alaskensis (after Tipton 1960), B — L. petrischevae (after Zemskaya and Lange 1979).

Fig. 7. L. petrischevae, male, spermatodactyl (after Zemskaya and Lange 1979).

A B

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Taxonomic status of Laelaps petrischevae

of the USSR Academy of Sciences, Novosibirsk. 440 pp. [In Russian]

Davydova, M.S., Nikolsky, V.V., Yudin, B.S., Dudareva, G.V., and Belova, O.S. 1980. [Gamasid mites of tundra of Middle Siberia]. In: M.S. Davydova (Ed.). Paraziticheskie nasekomyye i kleshchi Sibiri. Nau-ka, Novosibirsk, p. 141–148. [In Russian]

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Evans, G.O. and Till, W.M. 1979. Mesostigmatic mites of Britain and Ireland (Chelicerata: Acari, Para-sitiformes). An introduction to their external mor-phology and classification. Transaction of the Zo-ological Society of London, 35: 139–270.

Grant, C.D. 1947. North American mites of the genus Laelaps (Arachnida: Acarina: Parasitidae). Mi-croentomology, 12: 1–21.

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